Current and next generation optical networks are capable of transporting multiple wavelengths on the same fiber by using Dense Wavelength Division Multiplexing (DWDM) technology. Typical systems are capable of transporting thirty-two or more channels, at ten Gigabits per second (Gb/s) rate each. A wavelength division multiplexed optical transmission system employs plural optical channels, each channel being assigned a particular channel wavelength. In a WDM system, optical channels are generated, multiplexed to form an optical signal comprised of the individual optical channels, transmitted over a waveguide, and demultiplexed such that each channel wavelength is individually routed to a designated receiver.
Many networks today are based upon fiber-ring architectures, as evidenced by the proliferation of SONET/SDH time-division multiplexing (TDM) rings all the way from the long-haul backbone to the metropolitan and regional areas. Most large backbone rings represent significant investments on the part of service providers, and expectedly will have longer lifetimes. As a result, ring architectures will clearly play a major role in the evolution of optical networks. Given this large, entrenched base of ring topologies, currently many optical communication network operators are planning for a migration to equivalent dynamic optical ring architectures. Dynamic optical rings can be defined as fiber rings with dynamic lightpath provisioning capabilities such as routing, add/drop and protection. (A lightpath refers to the combination of the selected wavelength and path.) These optical wavelength routing rings, commonly also referred to as optical add-drop ring multiplexer (O-ADM) rings, will form the mainstay architecture for most metro/regional and even long-haul networks, helping operators ease their transition to future optical (mesh or hybrid ring-mesh) networks. Such systems typically include a plurality of nodes located along the ring. At least one optical add/drop element associated with each node is typically connected to the ring with optical connectors. The optical add/drop element permits both addition and extraction of channels to and from the ring. A particular node that allows the addition and extraction of all the channels is commonly referred to as a hub or central office node, and typically has a plurality of associated add/drop elements for transmitting and receiving a corresponding plurality of channels to/from other nodes along the ring.
In order to establish communication between any two nodes in an optical ring network both an appropriate path and an appropriate channel wavelength over which the information is to be conveyed must be selected. This task is performed by a routing and wavelength assignment algorithm that is typically implemented in a network management element. In most cases this network management element is the node itself. However it is also possible to implement the above mentioned algorithm in an external EMS (Element Management System) or NMS (Network Management System). Current algorithms generally employ a fixed set of criteria to determine the best route and wavelength, which are usually based on such factors as the shortest path between the nodes and the utilization rate and fragmentation of the various wavelengths. Since the algorithm is used network-wide to allocate resources for all the customers using the network, individual customers cannot select their own criteria that is of most importance to them. For example, one customer may wish to select a channel and path primarily on the basis of wavelength utilization efficiency, while another customer may wish to make the selection based primarily on the cost-savings that can be achieved by using a pre-existing transponder pack (TRP). This can currently only be achieved if the network management element can implement a different algorithm for different sets of criteria, which can be difficult and impractical to do.
Accordingly, there remains a need to implement a practical wavelength assignment and path selection process in a ring network in accordance with criteria that meets individual customers' specific needs rather than in accordance with a fixed set of criteria that are imposed on them.